1. Field of the Invention
The present invention relates to an organic light emitting display.
2. Description of the Prior Art
An organic light emitting display is a display that emits light by electrically exciting a fluorescent or phosphorescent compound and can display an image by driving N×M organic light emitting diodes. The organic light emitting diode includes an anode (ITO), an organic thin-film, and a cathode (metal). The organic thin-film is formed in a multi-layer structure including a light emitting layer EML that emits light when electrons are coupled with holes, an electron transport layer ETL that transports electrons, and a hole transport layer HTL that transports holes. The organic thin-film can also include an electron injecting layer EIL that injects electrons and a hole injecting layer HIL that injects holes.
As a method of driving the organic light emitting diode constructed as above, there are a passive matrix (PM) method and a metal oxide silicon (MOS) thin-film transistor (TFT) active matrix (AM) method. The passive matrix method is a method of driving using an anode and a cathode that perpendicularly cross each other and selecting lines. On the contrary, the active matrix method is a method of driving by connecting a thin-film transistor and a capacitor to each indium-tin-oxide (ITO) pixel electrode and maintaining a voltage using capacitor capacitance.
The organic light emitting display is used as a display device of a personal computer, a cellular phone and a personal digital assistant (PDA) or a display device of various information appliances.
Various light emitting displays having lower weight and volume than a cathode ray tube have been developed, and an organic light emitting display having excellent light emission efficiency, brightness and viewing angle and fast response time is being given attention.
A pixel circuit of an organic light emitting display is formed on a pixel area that is defined by two adjacent scan lines (or light emitting control lines) and two adjacent data lines. Here, if a scan signal (or light emitting control signal) is applied from two adjacent scan lines (or light emitting control lines), then an organic light emitting diode (OLED) of a pixel circuit emits light. Two adjacent scan lines (or light emitting control lines) electrically coupled with the pixel circuit, in case of an nth pixel circuit, can be an nth scan line (or light emitting control line) and an n−1th scan line (or light emitting control line). The scan line (or light emitting control line) electrically coupled with the pixel circuit applies a scan signal (or light emitting control signal) to an organic light emitting diode (OLED) of the pixel circuit, so that the organic light emitting diode (OLED) of the pixel circuit emits light and outputs images of one frame to a panel. However, because the images of one frame emit light concurrently in the organic light emitting display, it is possible to detect a pixel short only when a constant pattern is applied.
In a conventional pixel circuit, the short can be detected by applying a constant pattern to an organic light emitting display panel in a module process. However, a module process operation cost for a defective panel having a short is additionally needed. When a total inspection is not performed during the module process, reliability of the product is lowered because a longitudinal short cannot be detected as a defect during manufacturing, such that the defect is discovered by the end user of the product.